MUSEUM OF COxMPARATIVE ZOOLOGY. 75 



Halecium argenteum, sp. nov. 



Plate II. Figs. 18, 13. 



Trophosome. Stems and main branches polysiphonic, excepting at the outer 

 extremities. The stems are dark brown to black and stout at the base, becom- 

 ing lighter in color and luore delicate towards the tips. The outer parts of the 

 stem and branches are silvery white in color, being, when perfectly clean, 

 almost transparent under the microscope. The colonies are from an inch to 

 an inch and a half in height. 



The branches are like the stem, are irregularly arranged, and in two of the 

 four specimens lie nearly in one plane. The nodes are at about right angles, 

 and each internode bears a laterally projecting process near its upper end ; this 

 has a terminal opening surrounded by a rim ornamented with the row of 

 glistening dots so commonly found in the Haleciidse. Often a tubular process, 

 apparently a later growth, grows out of this opening ; it is composed of two 

 parts; the lower or proximal is small and thicker toward the inner or stem, 

 side (see Plate II. Fig. 12) ; the distal part is separated from the proximal by a 

 constriction, tapers slightly toward the base, has a simple terminal apei-ture, 

 slightly oblique, and usually shows the definite rim with its row of glistening 

 dots. 



Gonosome not present. 



Locality. Station 3384. About 100 miles south of the city of Panama. 

 Bathymetrical record, 458 fathoms. 



In the character of the internodes, and in the suppression of the hydrophores, 

 this species is allied to H. macroccphalum of AUman. Halecium Beanii is very 

 similar to them both. 



The .hydrophores are not always suppressed, for the secondary processes shown 

 in Figure 12 must be recognized as such. 



Sertularia variabilis, sp. nov. 



Plates IV., v., Figs. 17 to 22 inclusive. 



Trophosome. Stems sometimes simple, sometimes compound, slightly flexu- 

 ous, usually jointed at the flexures, main branches few and irregularly disposed; 

 a pinnate arrangement of the small branches is in some cases well marked. 

 Color, light horn. The hydrothecse are alternately arranged, usually one to an 

 internode ; they are largest near the base, have a tricuspid margin, which is 

 generally thickened and provided with a three-lobed valve ; they are strongly 

 divergent and very much exserted. The degree to which they are imbedded in 

 the stem varies greatly; in some instances they are scarcely more than attached 

 to the side of the stem, and in others are imbedded nearly a third of their length. 



Gonosome. The gonangia spring from just below the hydrothecse, are much 



